Free cutting structural steel

Grades, Chemical Compositions, and Mechanical Properties of Free-Cutting Structural Steels Free-cutting structural steels are widely used in the manufacturing of general machine tools and automatic machinery. These steels are available in both hot-rolled and cold-drawn forms, offering good machinability and mechanical performance. The following tables provide detailed information on their chemical compositions and mechanical properties. **Chemical Composition of Free-Cutting Structural Steels** | Brand | C (%) | Si (%) | Mn (%) | S (%) | P (%) | Pb (%) | |-------|--------|---------|---------|--------|--------|--------| | Y12 | 0.08–0.16 | 0.15–0.35 | 0.70–1.00 | 0.10–0.20 | 0.08–0.15 | - | | Y12Pb | 0.08–0.16 | ≤0.15 | 0.70–1.10 | 0.15–0.25 | 0.05 | 0.15–0.35 | | Y15 | 0.10–0.18 | ≤0.15 | 0.80–1.20 | 0.23–0.33 | - | - | | Y15Pb | 0.10–0.18 | ≤0.15 | 0.80–1.20 | 0.23–0.33 | 0.10 | 0.15–0.35 | | Y20 | 0.17–0.25 | 0.15–0.35 | 0.70–1.00 | 0.08–0.15 | ≤0.06 | - | | Y30 | 0.27–0.35 | 0.15–0.35 | 0.70–1.00 | 0.08–0.15 | ≤0.06 | - | | Y35 | 0.32–0.40 | 0.15–0.35 | 0.70–1.00 | 0.08–0.15 | ≤0.06 | - | | Y40Mn | 0.37–0.45 | 0.15–0.35 | 1.20–1.55 | 0.20–0.30 | ≤0.05 | - | | Y45Ca | 0.42–0.50 | 0.20–0.40 | 0.60–0.90 | 0.04–0.08 | ≤0.04 | Ca: 0.002–0.006 | *Note: The residual elements Ni, Cr, and Cu in Y45Ca steel should not exceed 0.25% by mass. When used for hot working, the copper content should not be more than 0.20%. Suppliers can guarantee this limit without analysis.* **Mechanical Properties of Free-Cutting Structural Steels (Hot-Rolled Strip)** | Brand | Tensile Strength (MPa) | Elongation δ5 (%) ≥ | Section Shrinkage Ψ (%) ≥ | Brinell Hardness HBS ≤ | |-------|--------------------------|------------------------|----------------------------|---------------------------| | Y12 | 390–540 | 22 | 36 | 170 | | Y12Pb | 390–540 | 22 | 36 | 170 | | Y15 | 390–540 | 22 | 36 | 170 | | Y15Pb | 390–540 | 22 | 36 | 170 | | Y20 | 450–600 | 20 | 30 | 175 | | Y30 | 510–655 | 15 | 25 | 187 | | Y35 | 510–655 | 14 | 22 | 187 | | Y40Mn | 590–735 | 14 | 20 | 207 | | Y45Ca | 600–745 | 12 | 26 | 241 | *Note: For steels with a diameter larger than 16 mm, the mechanical properties are measured from heat-treated blanks. For Y45Ca, the yield strength is not less than 355 MPa, tensile strength not less than 600 MPa, elongation δ5 not less than 16%, area shrinkage not less than 40%, and impact absorption energy not less than 39 J.* **Mechanical Properties of Cold-Drawn Free-Cutting Structural Steels** | Brand | Tensile Strength (MPa) | Elongation δ5 (%) ≥ | Brinell Hardness HBS | |-------|--------------------------|------------------------|---------------------------| | Steel Size (mm) | 8–20 | >20–30 | >30 | | Y12 | 530–755 | 510–735 | 490–685 | 7.0 | 152–217 | | Y12Pb | 530–755 | 510–735 | 490–685 | 7.0 | 152–217 | | Y15 | 530–755 | 510–735 | 490–685 | 7.0 | 152–217 | | Y15Pb | 530–755 | 510–735 | 490–685 | 7.0 | 152–217 | | Y20 | 570–785 | 530–745 | 510–705 | 7.0 | 167–217 | | Y30 | 600–825 | 560–765 | 540–735 | 6.0 | 174–223 | | Y35 | 625–845 | 590–785 | 570–765 | 6.0 | 176–229 | | Y45Ca | 695–920 | 655–855 | 635–835 | 6.0 | 196–255 | *Note: 1. For Y40Mn cold-drawn steel, after high-temperature tempering, the tensile strength is 590–785 MPa, elongation δ5 not less than 17%, and Brinell hardness HBS 179–229. 2. For steel wires with a diameter less than 8 mm, the mechanical properties and Brinell hardness are negotiated between supplier and buyer.* For more information, visit [www.chinawj.com.cn](http://www.chinawj.com.cn) Editor: Hardware Business Network Information Center

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